Lipophilization and molecular encapsulation of p-coumaric acid by amylose inclusion complex

p-Coumaric acid (CA) is a natural phenolic compound with a wide range of bioactivities, but its tendency to degrade during food processing and storage limits its application in functional foods. Forming amylose-guest inclusion complex is a technique to molecularly encapsulate guest molecules of interest and protect them from adverse environmental challenges. However, CA cannot be encapsulated into the helical cavity of amylose so this study used a strategy of lipophilization of CA to synthesize hexadecyl p-coumarate (HC), which might complex with amylose. The formation of the amylose inclusion complex was studied by complementary techniques: differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. To test the photo-stability of CA in the complex, a direct UV irradiation was performed. The in vitro release behavior of CA in the complex was also studied in both simulated gastric and intestinal fluids. The results showed that HC, but not CA, could form inclusion complex with amylose. Compared with CA, HC, and amylose-HC physical mixture, HC complexed with amylose showed a significant improvement in photo-stability (P < 0.05), with 90% retained, double the 43% retention of CA after 72 h of direct UV irradiation, and exhibited higher release rates of CA during in vitro digestion. These findings suggest that the amylose inclusion complex is a promising technique to protect CA in foods during processing and storage and to increase its bioaccessibility.